With the rapid expansion of markets for mobile type tablet terminals, smartphones, electric vehicles, stationary electricity storage systems, and the like, secondary batteries having excellent performance are required.
A method for producing a secondary battery is known in which after initial charge after a secondary battery is produced, the outer package is opened to vent the gas generated during the initial charge, and then the package is sealed again. By decomposing water that is included in a battery by initial charge and removing the generated gas from the package by this method, the effect of the water in the battery can be reduced.
For example, Patent Literature 1 discloses a method for producing a sheet type battery in which a gas generated during initial charge can be simply vented.
In addition, Patent Literature 2 discloses a method for producing a secondary battery by disposing electrodes and the like in a container, then removing water from the container, and subsequently preventing water from entering the container.
In addition, Patent Literature 3 discloses a method for producing a secondary battery, including a step of injecting an electrolytic solution, a step of initial charging, an aging step of storing in a predetermined temperature range, a pressing step, and a degassing and sealing step of venting a gas in an outer package made of sheet and sealing the package.
In addition, Patent Literature 4 discloses a method for producing a secondary battery, including a first injection step of injecting a first electrolytic solution containing a particular carbonate compound, a first charging step, a second injection step of injecting a second electrolytic solution containing a cyclic sulfonate, and a second charging step. It is described that by this, a film derived from the first electrolytic solution and a film derived from the second electrolytic solution are formed on a negative electrode active material layer in this order, and as a result, a secondary battery having excellent cycle characteristics is obtained.
In addition, Patent Literature 5 discloses a secondary battery including an opening and closing vent portion for releasing a gas generated by the decomposition of a nonaqueous electrolyte by charge and discharge. In addition, Patent Literature 6 describes a method of injecting an electrolytic solution in a plurality of portions.